1. Field of the Invention
This invention relates to abrasive articles comprising a thermoplastic or thermosetting binder which binds abrasive elements to a backing. The abrasive elements comprise abrasive particles partially embedded into a major surface of a metal binder.
2. Related Art
It is commonplace in both domestic and industrial applications to abrade the surface of a workpiece to achieve a desired finish. Conventional abrading operations are performed by the rapid rotation or reciprocation of abrading tools of various configurations, such as wheels, discs, belts and the like, against the surface to be finished. These tools include at least one abrasive surface comprising particles of an abrasive material embedded in a binder matrix which presents a multiplicity of tiny cutting edges to the workpiece.
During the abrading operation, individual abrasive particles are occasionally removed from the surface of the abrasive tool as a result of drag forces produced by contact between the tool and workpiece, which loosen and ultimately unseat the particles. This is referred to as "pull-out" or "shelling", the effects of which can vary from a simple reduction in cutting efficiency to uneven wear and the spoiling of the finish of the workpiece. For example, loose abrasive particles can mark the surface of the workpiece, necessitating further finishing operations to restore the desired finish.
Pull-out is most pronounced with coarse grain abrasives, especially when abrading hard materials, as larger particles are more susceptible to abstractive forces. Consequently, pull-out is a particular problem in the stoneworking industry where abrasive tools are used to shape and finish stone, such as marble, granite and the like.
The present invention seeks to provide abrasive articles having a reduced susceptibility to pull-out.
U.S. Pat. No. 4,256,467 (Gorsuch et al.) describes flexible abrasive articles and methods for their production. In one method, a stainless steel or other electrically conductive metal cylinder is coated with a resist material except at discrete areas. The cylinder is then wrapped in an electrically insulating mesh material, the cylinder and mesh emersed in an electrolytic bath, and metal deposited electrolytically from the bath over areas of the cylinder not having been coated with resist. The metal is deposited through the mesh material, and abrasive particles are added to the bath toward the end of the deposition time period, thereby providing areas of metal deposits having abrasive particles partially embedded therein.
U.S Pat. No. 5,127,197 (Bruxvoort et al.) describes similar articles, wherein the metal deposits are adhered to a backing using a metallic adhesive.
Also of background interest are U.S. Pat. Nos. 2,820,746; 2,492,143; 3,860,400; 4,047,902; 4,078,906; 4,111,667; 4,214,877; 4,288,233; 4,576,612, 4,798,026; 4,826,508; 4,863,573; 4,874,478; and 5,011,511, World Patent Application WO 90/00105 (published Jan. 11, 1990); UK Patent Applications 2 200 920 A (published Aug. 17, 1988) and 2 164 053 A (published Mar. 12, 1986); and British Patent Specifications 760,526 (published Oct. 31, 1956); 1 247 764 (published Sep. 29, 1971); and 1 458 236 (published Dec. 8, 1976). The background art discloses variations of and improvements to the Gorsuch et al. technology previously discussed; however, they do not disclose abrasive elements such as formed by Gorsuch et al. dispersed in a non-metallic binder in an abrasive article.
World Patent Application WO 79/00778 (published Oct. 18, 1979) discusses U.S. Pat. No. 2,216,728, which discloses abrasive aggregates comprised of diamond abrasive particles held together by sintering in the presence of metals such as nickel having an embrittling additive therein. The aggregates are said to be useful in resin bonded grinding wheels wherein the aggregates are surrounded by a resin phase.
The provision of a patterned abrasive surface to enhance grinding results is known in the art, as disclosed in the above-mentioned U.S. Pat. No. 2,820,746 and World Patent Application WO 90/00105, and more recently with the introduction of "patterned" abrasives made using rotogravure methods, such as those disclosed in U.S. Pat. Nos. 4,773,920 (Chasman et al.) and 5,014,468 (Ravipati et al.), and assignee's copending United States application Ser. No. 07/651,660, filed Feb. 6, 1991.
In reviewing the art to date one fails to discover abrasive articles comprising a thermoplastic or thermoset binder having abrasive elements dispersed therein, the abrasive elements comprising abrasive particles partially embedded into a major surface of a metal binder. Although the above-mentioned U.S. Pat. No. 2,216,728 describes metal-bonded diamond aggregate abrasives surrounded by a resin binder, the addition of embrittling additives (such as tin) to copper is apparently used to control the "slow but necessary breakdown of the metal bonded aggregate during use." This effectively increases, rather than decreases, pull-out of the abrasive particles, an objective diametrically opposed to that of the present invention.